docs: def asTuple(self):
          """Return the location as a tuple.
          Sort the dimension names alphabetically.
          ::
          
              >>> l = Location(pop=1, snap=-100)
              >>> l.asTuple()
              (('pop', 1), ('snap', -100))
          """
          t = []
          k = sorted(self.keys())
          for key in k:
              t.append((key, self[key]))
          return tuple(t)